Recently, there can be frequently seen a barrier, what is called, a high pole type barrier in which lifting poles that can be housed in a housing case placed under the ground are installed at entry and exit points of a car parking and the like.
Such general lifting pole apparatuses are so constructed that the poles are pulled up or put down manually. This operation is very troublesome, and hence the chances are that the poles unfavorably go out of use while they are still put down with the lapse of time. That is, in a case where the lifting pole apparatuses are installed in front of a car port, a user puts down the poles manually before getting in a car, and then gets the car out of the car port, thereafter pulls up the poles manually. In this way, the lifting and lowering operation of the poles are very troublesome, accordingly, they are still put down with the lapse of time, resulting in a useless and obstructive thing.
In a case where the parking space is of a private-use size, about two or three poles will suffice; however, in a case where the lifting pole apparatuses are used as a barrier for parking zones of a large-scale super market and the like, there are used a number of the lifting pole apparatuses. In that case, lifting and lowering the poles one by one manually will bring serious consequences.
Therefore, there is proposed a motor-operated type lifting pole apparatus which lifts and lowers a pole using a motor in order to make the operation simple and make the use easy. This conventional example is disclosed in Japanese Patent Application Laid-Open No. H10-53394, and Japanese Patent Application Laid-Open No. 2003-213636.
In a lifting pole apparatus disclosed in Japanese Patent Application Laid-Open No. H10-53394, a motor is disposed at a bottom portion in a housing case, an output shaft of the motor is engaged with a driving shaft, and the driving shaft extends along a center axis of the housing case. Further, a nut portion to be screwed on the driving shaft is disposed, and a pole is interlocked with the nut portion. The construction is that the rotation of the driving shaft by the motor causes the nut portion to move up and down along the driving shaft, which lifts and lowers the pole.
However, since the lifting pole apparatus disclosed in Japanese Patent Application Laid-Open No. H10-53394 is so constructed to drive, by the motor, the driving shaft extending along the center axis of the housing case over the total length, the motor has to be disposed in the housing case on its bottom portion. There is a possibility that rainwater and the like may enter into and accumulated in the housing case; accordingly, installing an electrical system including a motor on the bottom portion increases the possibility of the failures occurring.
To this end, there is disclosed in Japanese Patent Application Laid-Open No. 2003-213636 a construction which is capable of installing a motor at a relatively high level in a housing case. In this lifting pole apparatus, a stay for use in a driving mechanism including a motor comprises a column disposed upright on a bottom portion of the housing case, a flange formed on an upper end portion of the column, and a mounting base fixed to the flange. Thus disposing the stay and installing the driving mechanism at a relatively high level enables the electrical system to be protected even if water accumulates on the bottom.
In this construction, the motor is devised to drive a driving gear through an intermediate gear, both of which are rotatably supported on the stay. Further, the driving gear is threadably mounted on a screw shaft which hangs from a top portion of the pole inwardly; accordingly, the rotation of the driving gear causes the pole to lift and lower. That is, the motor serves as a driving system for driving the driving gear (nut), which has an inverted relationship to a case of Japanese Patent Application Laid-Open No. H10-53394 in which the motor serves as a driving system for driving the driving shaft. This makes it possible to dispose the electrical system including the motor on the stay at a relatively high level.
The motor used in the motor-operated type lifting pole apparatus mentioned above can be applied by only small-sized one which is capable of being housed in the housing case. In other words, a motor which is capable of being used has its limit in size, and hence an output torque of lifting and lowering the pole has its limit. To this end, it is recommended to make the pole, which is lifted and lowered by the motor, as light as possible.
On the other hand, from a viewpoint of recent terrorism-prevention countermeasures, there has been a demand of utilizing the lifting pole apparatuses as a barricade for preventing the vehicles from entering. That is, for the purpose of preventing a suicide bombing using a car, it is intended to install the lifting pole apparatuses, as traffic control means, on a road surface at entry and exit points of the important facilities, and then lift the poles as needed to thereby prevent the dangerous car from entering. But, in the above-mentioned conventional lifting pole apparatuses, the pole which is capable of lifting and lowering has its limit in weight; therefore, the pole having such a high strength as to stop the vehicle from colliding becomes, if it is desired to be realized, too heavy, which provides a problem that the existing apparatus cannot demonstrate an output torque required for lifting and lowering the pole.